Manufacture of biguanide derivatives



Patented Mar. 13, 1951 I DERIVATIVES Francis Henry Swinden Curd, deceased, late of Bramhall, England, by Muriel Ruth Curd, executrix, Branihall, England, and Dora Nellie Richardson, Manchester, England, assignors to Imperial Chemical Industries Limited, a corporation of Great Britain No Drawing. Application July 14, 1949, Serial No. 104,822. In Great Britain August 20,1948

4 Claims. 1 This invention relates to biguanide derivatives and more particularly it relates to the manufacture of biguanide derivatives which are useful as antimalarial agents.

The biguanide derivatives of antimalarial activity with which this invention is concerned are compounds of the formula:

wherein of X, Y and Z, one is chlorine, bromine or iodine and the others may be hydrogen, chlorine, bromine, iodine or lower alkyl radicals of 1-4v carbon atoms, and R is a lower alkyl radical v containing more than one and fewer than 8 carbon atoms.

Our invention comprises a process for the I manufacture of the said compounds which com-' prises interaction of a substance of the formula mNH-o-Nn-o-NHR Y T l i or its S-monoalkyl derivatives, with ammonia,

preferably in the presence of a desulphurising agent.

The starting materials may thus be the dithiobiurets of either of the S-monoalkyl derivatives thereof. It wil1 be understood that there are two S-monoalkyl derivatives thereof according as the alkylated sulphur is that adjacent to the nitrogen atom bearing thearyl group or that adjacent to th nitrogen atom bearing the alkyl group. The S-monoalkyl derivative in which the alkylated sulphur is that adjacent to the nitrogen atom bearing the alkyl group, viz. the l-aryl-5- a1kyl-4-a1kyldithiobiurets, may be made by interaction of an arylisothiocyanate with an N-alkyl- S-alkylisothiourea, and the corresponding l-aryl- 1-aryl-5-alkyldithiobiurets.

As desulphurising agents which are preferably used in the procees of the invention there are for example the oxides and salts of the heavy metals,

' particularly those of lead, copper, silver and mercury. Mercuric oxide is particularly suitable.

It may be supposed that the reaction proceeds by stages, the sulphur atoms being replaced stepwise. Thus in the second stage the reaction consists in the interaction of ammonia with a guanyl thioureaor with an S-substituted guanylisothiourea, in the presence of a desulphurising agent. This second stage of the process is described and claimed in British Patent No. 603,069.

The process of the invention is brought about by stirring and/or heating the reagents together. Conveniently this is carried out in presence of a solvent or diluent, for example methanol, ethanol or fl-ethoxyethanol.

The invention is illustrated but not limited by the following examples in which the parts are by weight.

Example 1 3.l5 parts of 1-p-chlorophenyl-5-isopropyl 4- ethylisodithiobiuret, 8.68 parts of mercuric oxide f and 50 .parts of ethyl alcoholic ammonia, saturated at room temperature, are stirred together at -35" C. for 20 hours. The reaction mixture is then filtered and the filtrate is evaporated to dryness under diminished pressure. The residue is extracted with 7% hydrochloric acid, the extract treated with carbon and filtered. The filtrate is made faintly alkaline to brilliant yellow with ammonia to precipitate N -p-chloropheny1- N -is0pr0py1biguanlde hydrochloride which crystallises from water as colourless needles, M. P. 243-2 i4. C. The corresponding base forms colourless rectangular plates from toluene, M. P. 129 C. and the actate, obtained by addition of acetic acid to an acetone solution of the base until the solution is faintly acid to litmus, crystallises from alcohol as colourless needles, M. P. 184- 185 C.

The starting material l-p-chlorophenyl-5-isopropyl l-ethylisodithiobiuret is prepared in the v following manner:

22.8 parts of N-isopropyl-S-ethyl-isothiourea hydrcbromide are added to a solution of 5.6 parts of potassium hydroxide in parts of Water, foland' the residue is washedwith water, dried and crystallised from light petroleum (B. P. -120 C.) and then has M. P. 122-124 C.

By working in a similar manner the followin (Examples 2-8) are obtained:

Example 2 N -p chlorophenyl N ethylbiguanide, M. P. 113-114" C. from 1 -p-chloropheny1-4-5-diethyl-4- isodithiobiuret. The starting material which is made as described above, by condensation of pchlorophenylisothiocyanate with N :S-diethylisothiourea hydrobromide crystallises from light petroleum (B. P. 100-120 C.) and has M. P. 110- 112 C.

Example 3 ,7'Z79 C. and is prepared from p-chlorophenyl isothiocyanate and N-n-butyl-s ethylisothiourea hydrobromide in the manner described above.

Example N --p-bromophenylN isopropylbiguanide hy- J drochloride, M. P. 246 C., from l-p-bromophenyl- 4-ethyl-5 isopropyl 4 isodithiobiuret which .is

,- made by condensing p-bromophenylisothiocyanate with N -isopropyl-S-ethylisothiourea hydrobromide as described above for the corresponding condensation using p-chlorophenylisothiocyanate and has M. P. 129-130" C.

Example 5 N -p-iodophenyl-N -isopropylbiguanide hydrochloride, M. P. 239 C. from l-p-iodophenyl-4- ethyl-S-isopropyl i isodithiobiuret which crystallises from light petroleum (B. P. 100-120 C.)

and has M. P. m l-125 C. It is prepared by con-- densation of p-iodophenylisothiocyanate with N- isopropyl S ethylisothicurea hydrobromide in aqueous alcoholic alkaline solution.

Example 7 N -mchlorophenyl-N -isopropylbiguanide hydrochloride, M. P. 232 C. from i m chlorophenyL-ethyl-5 isopropyl 4 isodithiobiuret. The starting material may be made by the condensation of n1-chlorophenylisothiocyanate with N-isopropyl-S-ethylisothiourea hydrobromide in aqueous alkaline solution and crystallises from lightpetroleum (B. P. 60-80 C.). It has M. P. 80-81 C. l

Example 8 -Bz l dichlorophenyl N Q isopropylbiguanide hydrochloride, M. P. 244445 c. from 1- 3':4'-dichlorophenyl 4 ethyl-5 isopropyl 4- isodithiobiuret which crystallises from light pe- 'troleum (B. P. Bil-100 C.) and has M. .P. l04.-l05

C. It is obtained by condensation of 3;4-dichlorophenylisothiocyanate with N-isopropyl-S- v ethyl-isothiourea hydrobromide in aqueous alkaline solution.

Example 9 2.85 parts of l-p-chlorophenyl 5 isopropyldi thiobiuret, 8.68 parts of mercuric oxide and 100 parts of alcoholic ammonia, saturated at room temperature, are stirred together at -35" C. overnight. The reaction mixture is filtered and the filtrate is evaporated to dryness under reduced pressure. The residue is dissolved in acetone and the solution is made acid to litmus with Aceti ac d. er ist u q t ii ed. N -s-. h .0r.

4 phenyl-N -isopropylbiguanide acetate which has M. P. 184-185 C.

The starting material 1p-chlorophenyl-N isopropyldithiobiuret is prepared as follows:

0.92 part sodium is dissolved in 25 parts of ethyl alcohol and hydrogen sulphide is passed in until the gain in weight is 1.36 parts. This solution is added to a suspension of 6.3 parts of l-pchlorophenyl- 4 -ethyl- 5 -isopropyl-4 -isodithiobiuret in 56 parts of alcohol and the mixture is boiled under reflux for 1 hour with the continual passage of hydrogen sulphide through the mixture. The resulting solution is treated with carbon, filtered and acidified with acetic acid. On cooling l-p-chlorophenyl-5-isopropyldithiobiuret separates and is collected and crystallised from light petroleum. It has M. P. 148 C.

By working in a corresponding manner the following (Examples 10-16) are made:

Example 10 N -p-chlorophenyl-N -ethylbiguanide, M. P. 113-1l4 C., from 1-p-chlorophenyl-fi-ethyldithiobiuret which is prepared by thiohydrolysis, as described above, of l-p-chlorophenyllzfi-diethyl-*l-isodithiobiuret and has M. P. 158-l60 C.

Example 11 N -p-chlorophenyl-N -n-propylbiguanide, M. P. 59-60 C., from l-p-chlorophenyl-S-n-propyldithiobiuret which is prepared by thiohydrolysis of 1-p-chlorophenyl-4-ethyl-5-n-propyl-4-isothiobiuret and has M. P. 140-141 C.

Example 12 N --p-chlorophenyl-N -n-butylbiguanide hydro chloride, M. P. 208" C., from l-p-chlorophenyl-fin-butyldithiobiuret which is prepared by thiohydrolysis of l-p-chlorophenyl-4-ethyl-5-n-butyli-isodithiobiuret and has M. P. 132-133 C.

Example 13 N -m-chlorophenyl-N -isopropylbiguanide hydrochloride, M. P. 232 C., from l-m-chlorophenyl-5-isopropyldithiobiuret which is prepared by thiohydrolysis of 1-m-chlorophenyl-4-ethyl- 5-isopropyl-4-isodithiobiuret and has M. P. 128- 129 C.

Example 14 N -p-iodophenylN -isopropylbiguanide hydrochloride, M. P. 239 C., from 1-p-iodophenyl-5- isopropyldithiobiuret, M. P. 136-138 C., which is prepared from 1-p-iodophenyl-4-ethy1-5-isopropyl-4-isodithiobiuret by thiohydrolysis with sodium hydrosulphide in alcoholic solution saturated with hydrogen sulphide.

Earample 1 5 'isopropyl-4-isodithi0biuret and has M. P. 150- 152C.

Example 16 N -3 4-dichlorophenyl- N -isopropylbiguanide hydrochloride, M. P. 2 :4-245 C. from 13:4'-dichlorophenyl-5isopropyldithiobiuret which has M. P. 158 C. and is prepared by thiohydrolysis of l- 3':4'-dichlorophenyl 4 ethyl-.5-isopropy1- lisodithiobiuret.

Example 1? 2.55 parts of l-p-chlorophenyl-2-ethyl-5-isopropyl-2-isodithiobiuret, 7.1 parts of mercuric oxide and 50 parts of alcoholic ammonia, saturated at room temperature, are stirred together at 30-35 C. for 20 hours. The reaction mixture is filtered and the filtrate is evaporated to dryness under reduced pressure. The residue is extracted with warm 2 N-hydrochloric acid and the extract is filtered. The filtrate is made faintly alkaline to brilliant yellow with ammonia and a little common salt is added. The precipitated product is filtered off and crystallised from water to give N -p-chlorophenyl-N -isopropylbiguanide hydrochloride, M. P. 243-244 C.

The starting material l-p-chlOrophenyl-Z-ethyl-5-isopropyl-2-isodithiobiuret is prepared by mixing 8.6lparts of 1ep-chlorophenyl-5-isopropyldithiobiuret, 5.15 parts of ethyl iodide, 150 parts of ethyl alcohol and 3 parts of 0.880 ammonia, and. allowing the mixture to stand for 3 days. The resulting solution is evaporated under reduced pressure and the residue is crystallised from light petroleum (B. P. (SO-80 C.) to give 1-pchlorophenyl- Z-ethyl- 5 -isopropyl- 2 -isodithiobiuret which has M. P. 82-84" C.

We claim:

1. A process for the manufacture of biguanide derivatives of the general formula:

Y NE NH wherein X is a halogen radical of atomic weight greater than fluorine, Y and Z are radicals from the group consisting of hydrogen, halogen of atomic weight greater than fluorine, and lower alkyl having between 1 and 4 inclusive carbon atoms, and R is a lower alkyl radical having between 2 and 7 carbon atoms inclusive, which comprises mixing a substance from the group consisting of those having the general formula:

ggm m m wherein the symbols have the significance stated above, and the S-monoalkyl derivatives thereof, with ammonia, allowing the intermixed materials to react and recovering the biguanide derivative from the reaction product.

2. A process as claimed in claim 1 wherein said intermixed materials are allowed to react in the presence of a desulphurizing agent from the group consisting of heavy metal salts and heavy metal oxides.

3. A process as claimed in claim 1 wherein the reaction between said substance and ammonia is allowed to progress in the presence of an inert solvent.

4. A process as claimed in claim 1 wherein the ammonia is in the form of a solution in an inert solvent when it is mixed with said substance.

MURIEL RUTH CURD, Executrim of the Estate of Francis Henry Swinden Curd, Deceased.

DORA NELLIE RICHARDSON.

REFERENCES CITED The following references are of record in the file of this patent:

Fromm: Liebigs Annalen, vol. 394 1912), page 

1. A PROCESS FOR THE MANUFACTURE OF BIGUANIDE DERIVATIVES OF THE GENERAL FORMULA: 